1. Field of the Invention
The present invention relates to a process for producing a thin soft-magnetic alloy film having a high saturation magnetic flux density for use in high density magnetic recording and reproducing heads.
2. Description of the Related Art
Magnetic head materials effective as recording mediums having a high coercive force (Hc) as required for high density magnetic recording has to exhibit a high saturation magnetic density (Bs). As conventional soft-magnetic materials for thin film magnetic heads having a high Bs value, those which can be produced by an electrodeposition technique capable of patterning at a high accuracy through a low temperature process are limited to a binary Ni-Fe alloy (Permalloy) having a Bs value as Bs.perspectiveto.9,000 Gauss. In order to more sufficiently improve the magnetic recording and reproducing efficiency of the magnetic heads, however, it is desired that a thin film having a higher Bs value and excellent soft-magnetic properties can be produced by such an electrodeposition technique as having the same advantages as that for production of Permalloy.
Though thin ternary Fe-Co-Ni alloy films exhibit an extremely high Bs value when Bs=10,000 to 21,000 Guass and have excellent soft-magnetic properties, each of the components of the electrodeposited alloys has its own order at which it is preferentially deposited in a deposition sequence of the components and therefore, deposition of a plurality of components (as alloy deposition) is frequently difficult, or, if it is possible, control of the composition has many limitations. Specifically, no technique for electrodepositing thin films of a ternary alloy such as a Fe-Co-Ni system has been known heretofore.
Primarily, in electrodeposition of respective components from a solution containing ions such as Fe, Ni and Co, potentially noblest ions are expected to be preferentially deposited. As can be observed in electrodeposition of the known binary Fe-Ni alloy, a complex reaction such as discharge of H.sup.+ ion is associated on a cathodic electrode during the electrodeposition so that there is a problem of an increase of pH value in the vicinity of the cathodic electrode. That is, since each ion is discharged and electrodeposited through a layer of Fe hydroxides stable at a high pH value in the vicinity of the cathodic electrode, it is considered possible for component ions to be co-deposited during the electrodeposition (anormal co-deposition). For this reason, actually a variety of alloy compositions may be electrodeposited depending upon a ratio in concentration of ions in the electrodepositing bath.
The ratio of elements in electrodeposited alloy films may depend naturally upon various electrodeposition conditions such as a pH value throughout the electrodepositing bath, a current density at a cathode and the like, interalia, greately upon a ratio of respective ion concentrations (the absolute ion concentrations of respective components are not critical).
If a ratio of divalent Fe ion (Fe.sup.2+) to other ions is too high, the influence of the Fe ion on the Fe hydroxide layer at the cathode at the time of Fe ion discharge offers primarily problems as described above, such as surface roughness due to the incorporation of oxidized Fe in the electrodeposited films, occurrence of adverse effect on the stable discharge of other ions (Co.sup.2+, Ni.sup.2+) resulting in instability of film composition and incapability of electrodeposition of the ternary alloy.